Electromagnetic sound reproducer



Patented Feb. 17, 1925.

UNITED srar as' PATENT OFFICE.

CECIL BBIGHAM, OF EAST GRANGE, NEW JERSEY, ASSIGNOR TO C. BBANDES, INC.,

' 0F NEW YORK, N. Y., A CORPORATION 0F NEW YORK.

ELECTROMAGNETIC SOUND REPRODUGER.

Application filed March 13, 1924. Serial No. 699,167.

to' provide an extremely simple electrov magnetic sound reproducing mechanism which will have the characteristic 0faccurate sound reproduction where instruments are made inl large numbers and where uniformity and permanency of product is of supreme importance.

'-Another object of4 my invention is to provide -a mounting for the diaphragm in an electromagnetic sound reproducing mechanism in which uniform distance bevtween the magnets and the'diaphragm 1s insured where instruments are manufac-y Ytured on a quantity production basis, the

mounting bein so arranged that a cap in which the diap ragm may becentered may be forcibly screwed' down upon the electromagnetic casing to lock the diaphragm in permanent operating position, eliminating all necessity of adjusting the instrument after it has initially passed careful factory inspection. p

A further object of my inventionis to provide a resilient'peripheral mounting for the diaphragm in the electromagnetic mechanism on each .side thereof, the resilient mounting being such that the resilient characteristic is permanently, maintained by reason of the peculiar characteristics of the resilient material which Iy have discovered for eilicient operation of the electromagnetic sound reproducer.

Other and further objects of my invention will be understood from the specilication hereinafter following by reference to the accompanying drawings, in which:

Figure l is a cross-sectional view taken through the electromagnetic sound reproiducer-pof my invention; Fig. 2 is a frag-"- mentary cross-sectional view showing one method which I may employ for mounting the diaphragm in the instrument; and Fig.

3 isa cross-sectional view showing another method which I may employ for mountin the diaphragm in the instrument. l

Heretofore in the art ordinary telephone receivers have generally been used in the construction of reproducers in radio receiving apparat-us.` There has been little change in such telephone receivers since the early days of line Wire telephony, and there has been a marked deficiency in radio reproduction due to the lack of analysis of the special problems existing in radio reproduction. I have studied the requirements in electromagnetic sound reproducers, taking into consideration both the alternating current component and the direct current component existing in the output plate circuit of an audio frequency electron tube amplifier, and I have selected an efiicient construction of sound reproducer in which a pair of electromagnets is positioned in a casing with anextremely small grinding depth. I provide a cap, screw threaded to engage the casing, with an integral annular ring located within the cap in such manner that in the assembly process a re- ,silient ring, the diaphragm, and a second resilient ring, may be readily centered therein without ythe exercise of any high degree of skill, andthe ca screwed over the casing and firmly anc ored thereon. The resilient mounting which I provide for the diaphragm isthe result of considerable investigation. A fabric linen ring having a rubberized surface thereonis employed. rl `he ring is extremely thin and the rubber and fabric are each substantially in the natureof a film. The fabric serves to give body to the rubber film and to permanent- -ly preserve the same. The rubber, although it is minute in thickness, provides just the amount of resilience which I have found to be necessary in my construction. In assembling the rings and the diaphragm the rubber surfaces of the cloth rin s are placed directly adjacent the diap ragm while the cloth `surfaces are positioned directly adjacent the periphery of the casducing mechanism and also directly adjacent the centering ring within the cap of the casing. i

ing of the electromagneticl sound repro- Referring more particularly to lthe drawings, reference character 1 indicates the casmg which houses the electromagnetic opermagnet coils 4 and 5 respectively. Permanent magnets 6 and 7-'are positioned around the'interior of the `casing 1 forming magy netic circuits with pole pieces 2 and 3. The

combined in an integral body.

permanent magnets are maintained in position by means of kidney members 8 and 9 respectively, being secured to the casing'l b y means of screws' 8a and 9a. The terminals fromthe magnet windings are brought out to binding posts 10 and 11. The periphery 12 of casing 1 is ground in a plane extremely close to the plane of thepole tips of the pole pieces 2 and 3. A screw cap 14 is provided having an annular depending skirt 15 containing the interior screw threads which engagewith exterior screw threads on casing 1. rlhe screw cap 14 is thickened in its central portion as represented by reference character 16 and annular flange 17 provided around screw threaded aperture 18 in the center of cap-14.

YThe .screw threaded aperture is provided with an annular counterbored portion 19 immediately adjacent the ilange 17 enabling a 'errule 2O to be screw threaded into the aperture 18 and irmly seated with its shoulder 21 against' the top surface of liange 17. The fel-rule 20 serves as a seat and support for the acoustic horn 22.

. The cap 14 is provided with an integral depending annular ring 23 on its lower face thereof. Anvertical Wall portion 24 is vided in the niolded cap 14 immediately adjacent its interior surface and spaced from the screw threads on the interior of the. cap to provide means for centering the -diaphragm mounting-within'the cap before the casing 1 is engaged therewith.

The resilient mounting com rises a pair of annular rings 25 and 26. ach ring is made up of two dissimilar materials formed integral with each other which 1 have selected for inost ecient operation. Each ring comprises a fabric sheet A and a rubber lm B. The fabric sheet and rubber film are substantially molded to ether or oth the fabric and the rubber is extremely thin. The rubber surface of each ring is placed immediately adjacent the diaphragm 27 while the fabric lsurfaces contact with the periphery 12 of casing 1 and the lowersurface of the depending iange 23 of cap 14. The rubber film serves to resiliently support the diaphragm and permit relatively large vertical movement thereof. The rubberized ring 25 is centered in the cap 14 in Ythe 'construction illustrated in Fig. 2 by .match-ingritwith they-edge. of the depending 4integralring'23. The. diaphragm 27 is then ljilacedin-position upon the rubber' surface of the ring 2'5 and next the rubberized ring 26 is centered upon the underside of resaca@ the diaphragm, being guided at its periphery by the first of the screw threads in the skirt 15, as illustrated in Fig. 2.

1n Fig. 3 1 have shown -a construction i which enables the rings 25 and 26 and diaphragm 27 'to be readily assembled within the vertical wall space 24 in the cap 14. It will be appreciated that this construction is such as to permit unskilled labor to readily assemble the reproducer. IThe casing 1 may then be screwed into the lskirt 15 of capr14 and firmly tightened in position. No adjustments are required after the initial setting, the particular formation of the rings 25 and 26 adording the required amount of resiliency when the casing 1 is screwed into cap 14 under predetermined pressure.

Again 4referring yto F ig. 1 l provide an annular space 28 beneath the skirt of the cap 14 in which a sealing material may be introduced to prevent tampering with the -instrument after it has passed factory inspection. 7lhe lower edge of the skirt 15 may be provided with depending tongues 29 to facilitate mounting the instrument in a base.

The present embodiment of my linvention Ihas been found to be particularly eflicient in operation and practical in construction. The instrument is operated from the output circuit of an electron tube radio receiving a paratus without the employment of an ad itional energy supply sourcel necessary in' f ters Patent of the United States is as follows:

, 1. An electromagnetic sound reproducer, comprising in combination an electromagnctic operating mechanism, a casing containV ing said mechanism, a diaphragm, and resilient means for supporting said diaphragm upon said casing comprising a pair of relatively thin rings, one positioned on one side of said diaphragm and the other on the opposite side thereof, each of said rings comprising layers of dissimilar material formed integral with each other, and means forclamping said rings and diaphragm in clamping said rings andv diaphragm on said casing.

An 'electromagnetic sound reproducer, comprising in combination an electromagneticoperating mechanism, a casing enclosing said mechanism, a diaphragm, means for supporting said diaphragm on said casing relative to said electromagnetic operating mechanism comprising a pair of rings, one located on one side of said diaphragm and the other on the opposite side thereof, eac-h of said rings comprising a layer of rubber and a layer of cloth formed integral with each other with the rubber layers im-l mediately adjacent said diaphragm, and means for clamping said rings and diaphragm upon said casing.

4. An electromagnetic sound reproducer, comprising in combination a casing, an electromagnetic operating mechanism in said easing, a diaphragm, a screw threaded cap engaging said casing at. its periphery, said Cap having a short vertical Wall portion adjacent its inner surface, and a resilient mounting for said diaphragm adapted to be centered within said short vertical Wall portion, said mounting consisting of a pair of rlngs each comprising alternate layers of' different material formed integral with each other with one.of said rings located on one side of said diaphragm and the other of said rings located on the opposite side of said diaphragm.

5. An electromagnetic sound reproducer, comprising in combination a casing, an electromagnetic operating mechanism in said casing, a diaphragm, -a screw threaded cap engaging said casing at its periphery, said cap having a short Vertical Wall portion adjacent its inner surface, and a resilient mounting fork said diaphragm adapted to be centered Within said short Vertical wall portion, said mounting consisting of a pair of rings each comprising alternate layers of different material molded one into the other to form a substantially integral body having a rubberized surface, with one of said rings located on one side of said diaphragm and the other of said rings located on the opposite side of said diaph agm.

CECIL E. BRIGHAM. 

